“Morphine is a potent opioid analgesic used to alleviate moderate or severe pain but the development of drug tolerance and dependence limits its use in pain management. Previous studies showed that cannabinoid type 2 (CB2) receptor ligands may modulate opioid effects. However, there is no report of the effect of CB2 receptor agonist on acute morphine tolerance and physical dependence. We therefore investigated the effect of a CB2 receptor agonist (AM1241) on morphine-induced morphine tolerance and physical dependence in mice. Our findings suggest that coadministration of the CB2 receptor agonist and morphine could increase morphine antinociception and reduce morphine tolerance and physical dependence in mice.
Category Archives: Endocannabinoid System
Molecular and cellular basis of cannabinoid and opioid interactions.
“Cannabinoids and opioids have been shown to possess several similar pharmacological effects, including analgesia and stimulation of brain circuitry that are believed to underlie drug addiction and reward. In recent years, these phenomena have supported the possible existence of functional links in the mechanisms of action of both types of drugs.
The present review addresses the recent advances in the study of biochemical and molecular mechanisms underlying opioid and cannabinoid interaction. Several hypothesis have been formulated to explain this cross-modulation including the release of opioid peptides by cannabinoids or endocannabinoids by opioids and interaction at the level of receptor and/or their signal transduction mechanisms.
Moreover it is important to consider that the nature of cannabinoid and opioid interaction might differ in the brain circuits mediating reward and in those mediating other pharmacological properties, such as antinociception.
Further studies are needed since a better knowledge of the opioid-cannabinoid interaction may lead to exciting therapeutic possibilities.”
https://www.ncbi.nlm.nih.gov/pubmed/15927245
https://www.sciencedirect.com/science/article/pii/S0091305705001450?via%3Dihub
Opioids and cannabinoids interactions: involvement in pain management.
“Among several pharmacological properties, analgesia is the most common feature shared by either opioid or cannabinoid systems.
Cannabinoids and opioids are distinct drug classes that have been historically used separately or in combination to treat different pain states.
Indeed, it is widely known that activation of either opioid or cannabinoid systems produce antinociceptive properties in different pain models.
Moreover, several biochemical, molecular and pharmacological studies support the existence of reciprocal interactions between both systems, suggesting a common underlying mechanism.
Further studies have demonstrated that the endogenous opioid system could be involved in cannabinoid antinociception and recent data have also provided evidence for a role of the endogenous cannabinoid system in opioid antinociception.
These interactions may lead to additive or even synergistic antinociceptive effects, emphasizing their clinical relevance in humans in order to enhance analgesic effects with lower doses and consequently fewer undesirable side effects.
Thus, the present review is focused on bidirectional interactions between opioids and cannabinoids and their potent repercussions on pain modulation.”
https://www.ncbi.nlm.nih.gov/pubmed/20017728
“Cannabinoids and opioids are distinct drug classes historically used in combination to treat pain. Delta(9)-THC, an active constituent in marijuana, releases endogenous dynorphin A and leucine enkephalin in the production of analgesia.
The endocannabinoid, anandamide (AEA), fails to release dynorphin A. The synthetic cannabinoid, CP55,940, releases dynorphin B. Neither AEA nor CP55,940 enhances morphine analgesia. The CB1 antagonist, SR141716A, differentially blocks Delta(9)-THC versus AEA. Tolerance to Delta(9)-THC, but not AEA, involves a decrease in the release of dynorphin A.
Our preclinical studies indicate that Delta(9)-THC and morphine can be useful in low dose combination as an analgesic. Such is not observed with AEA or CP55,940.
We hypothesize the existence of a new CB receptor differentially linked to endogenous opioid systems based upon data showing the stereoselectivity of endogenous opioid release. Such a receptor, due to the release of endogenous opioids, may have significant impact upon the clinical development of cannabinoid/opioid combinations for the treatment of a variety of types of pain in humans.”
“Cannabinoids and opioids both produce analgesia through a G-protein-coupled mechanism that blocks the release of pain-propagating neurotransmitters in the brain and spinal cord. However, high doses of these drugs, which may be required to treat chronic, severe pain, are accompanied by undesirable side effects.
Thus, a search for a better analgesic strategy led to the discovery that delta 9-tetrahydrocannabinol (THC), the major psychoactive constituent of marijuana, enhances the potency of opioids such as morphine in animal models.
In addition, studies have determined that the analgesic effect of THC is, at least in part, mediated through delta and kappa opioid receptors, indicating an intimate connection between cannabinoid and opioid signaling pathways in the modulation of pain perception.
A host of behavioral and molecular experiments have been performed to elucidate the role of opioid receptors in cannabinoid-induced analgesia. The aim of such studies is to develop a novel analgesic regimen using low dose combinations of cannabinoids and opioids to effectively treat acute and chronic pain, especially pain that may be resistant to opioids alone.”
“The endogenous 
“Cannabinoids are naturally occurring compounds, derivatives of Indian hemp, in which tetrahydrocannabinol (THC) is the most important. Marijuana, hashish and hash oil are among those most commonly used in the group.
Cannabinoids (marjhuana and hashish) have been used throughout recorded history as effective drugs in treating various diseases and conditions such as: malaria, hypertension, constipation, bronchial asthma, rheumatic pains, and as natural pain relief in labour and joint pains.
Marijuana acts through cannabinoid receptors CB 1 and CB2. Both receptors inhibit cAMP accummulation (through Gi/o proteins) and stimulate mitrogen- activated protein kinase. CB1 rceptors are located in CNS and in adipose tissue, digestive tract, muscles, heart, lungs, liver, kidneys, gonads, prostate gland and other peripheral tissues. CB2 cannabinoid receptors are located in the peripheral nervous system (at the ends of peripheral nerves), and on the surfaces of the cells of the immunological system.
The discovery of endogenous cannabinoids has contributed to a better understanding of their role in the regulation of the intake of food, energetic homeostasis and their significant influence on the endocrine system.”